[missouri100]

I have a little 4 wire 2 phase stepper motor that turns 7.5 deg per step. I think it is from a plotter or something (ebay purchase). Max voltage is 24V and I am running it, or trying to, at 12v. I checked the leads to find which wires go to which coils. The problems is at some of the step locations it has very little holding torque while other locations it has quite a bit of holding torque. It also doesn't seem to have much torque when making the step to a weak location. It steps odd also sometimes. I have spent a fair amount of time trying to determine the "firing order" and I can't seem to find one that provides a smooth continuous stepping. I am using a L298N Dual H Bridge stepper controller. The same circuit works fine on other bipolar motors I have used it on. Considering I got basically the same resistance for both coils I would think the motor was OK. Do these symptoms point to a motor issue, incorrect "firing order", or something else?

Any suggestions will be appreciated. I need it for a high school science olympiad project that I am helping with and we are getting close to the deadline.

thanks

[awerby]

Stepper motors are often marked with a "nameplate voltage" that is much less than the voltage they actually run best at. Are you sure that 24v is the max voltage this motor can take? Do you have any other specs for the motor? You can also figure out the optimum supply voltage from the inductance, if you've got that. On a 2-phase motor, the firing order is a simple alternation of phases A and B.

[missouri100]

here is an image of the motor. the 24v value came from the ebay listing so who really knows if that is correct.
I just googled it and the only info is on alibaba where they are selling them by the thousands. All the specs in the ebay listing checked out and that is all there is.

http://www.cnczone.com/forums/attach...d=303086&stc=1

[jeffrey001]

Current is more related to torque while voltage is for rpm.

Can you controller be adjusted for current?

Jeff

[missouri100]

no. it draws whatever the coil winding resistance allows for a given voltage - that is until the magic smoke appears from the controller. The coil resistance is 16 ohms so at 12 volts it should draw about .75A. The controllers is rated for 2A max but I have another motor drawing about 1.5A and the controller gets pretty hot. I suspect the .75A is pretty accurate.